Process for consolidating fibres



United States Patet 3,025,203 Fatented Mar. 13, 19fi2 3,025,203 PROCESS FOR CONSGLIDATHNG FlBlREfi Curt Walter Leupold and Rolf Mohr, Nurnberg, and Kurt Sponsel, Krefeld, Germany; said Leupold assignor to Vereinigte Papierwerke Schiekedanz & Co., Numberg, Germany, a corporation of Germany No Drawing. Filed Dec. 26, 1957, Ser. No. 705,116 3 Claims. (Cl. 156-36) fibers can be consolidated by employing synthetic resins,

such as the polyvinyl acetates, styrol polymers, and ureaformaldehyde combinations. But securing adequate consolidation of the fibers in this manner requires the employment of such quantities as to impart a stiff, in fact,

boardlike character to the end product as a rule, which thus possesses no absorbency. Up to the present time no suitable consolidation agent has been found for manufacturing fiber products that are waterproof and yet absorbent, while possessing high breaking strength transversely and longitudinally.

In the invention absorbent though waterproof fiber products are produced to solve this problem by applying, especially by spraying, aqueous solutions of formaldehyde, urea, or urea derivatives and methylcellulose to the fibers to be fastened together. The water is then evaporated olf, and the fibrous material is heated, allowing for its resistance to heat. It is advisable to add a hardening catalyst to this aqueous solution in known manner before it is sprayed. Various chemical reactions take place when a solution consisting of the four substances mentioned is employed.

Not only do urea and formaldehyde react together in known fashion, but the traces of formaldehyde that escape during heating also react with the methylcellulose as well as with cellulose fibers when the latter are employed. Though methylcellulose as such is water-soluble, it thus enters into water-insoluble compounds with the other constituents. The resulting substances are tough and resilient and adhere very firmly to the fibers. As the water-insoluble plastic coating is first formed on the fiber, the fibers enveloped by the resulting plastic film are fastened together very well. The fibers, which exist preferably with random orientations, thereby adhere considerably to one another at their points of contact. This produces a fabriclike structure, though unwoven, which exhibits the desired properties: It is absorbent and posssesses satisfactory mechanical properties, which it retains even in the presence of moisture or water. In the invention the high breaking strength in the wet and the dry state is achieved with a coating that is so thin that the end product possesses satisfactory pliability.

If an especially soft feel is required, the fibrous materials feel may be improved in the known manner by adding glycerol or similar agents. One advantageous application of the process covered by the invention is that the fibers are processed in a state of suspension during flocking or carding.

Another application is treating merely the surface of molded structures made of fibrous material with the process of the invention.

It is often necessary and desirable to impregnate the product in one way or another, care being taken that the more volatile substances do not escape prematurely. In

the invention these additives, such as pigments, perfumes, dyes, impregnating agents, or active substances that possess, say, deodorizing, disinfecting, or bactericidal action, may be added to the aqueous solution described above and thus sprayed on together with the latter. More particularly, when they are not water-soluble, they may be applied subsequently, before the heat treatment. This presupposes that they can be subjected to this heat without suffering damage.

The following examples are cited of the suggestions in accordance with the invention:

Example 1 2000 grams methylcellulose 500 grams urea-formaldehyde pro-condensate 500 ml. glacial acetic acid 1000 grams glycerol are dissolved in liters of water and sprayed on a celluose fiber fleece weighing 20 g. per sq. m. in such a manner that 50 gram-s of sprayed liquid are applied to 1 sq. m., equivalent to a dry substance of about 1.3 g. per sq. in.

Example 2 2000 g. methylcellulose 1600 g. melamine-formaldehyde-resin pre-oondensate 400 g. ammonium oxalate 500 g. concentrated sorbitol solution 100 g. mercury oxycyanide are dissolved in 100 liters of water. This solution yields excellent consolidation of cellulose fibers, besides possessing very good germicidal action. The active antibacterial agent is imbedded in the plastic layer and exhibits high surface-active strength despite its low concentration.

In addition to its favorable physical properties mentioned, the product of the process covered by the invention also possesses the advantage, in contrast to fibrous materials consolidated by known processes, of not irritating the skin. Hence, products made in accordance with the invention are highly adapted, say, for use as wrappers for sanitary napkins or for so-called paper handkerchiefs or for all articles that come in contact with the human or animal mucosa.

We claim:

1. A process for consolidating cellulose fibres to produce a matted unwoven material, said method comprising the steps of applying to the fibres an aqueous solution containing formaldehyde, methyl cellulose, and a substance selected from the group consisting of urea and urea derivatives, the content of methyl cellulose in said solution being greater than that of any of the other ingredients.

2. A process, as recited in claim 1, in which a hardening catalyst is incorporated in the aqueous solution.

3. A process, as recited in claim 1, in which the aqueous solution is sprayed onto the fibres while in a state of suspension.

References Cited in the file of this patent UNITED STATES PATENTS 70,18 Bass et al Ian. 13, 194 2,339,562 Eustis Ian. 18, 1944 2,400,533 Buffington May 21, 1946 ,462,253 Booty Feb. 22, 1949 8 Heritage Sept. 9, 1952 ,167 Cone Oct. 7, 1952 FOREIGN PATENTS ,798 Great Britain Jan. 23, 1957 

1. A PROCESS FOR CONSOLIDATING CELLULOSE FIBERS TO PRODUCE A MATTED UNWOVEN MATERIAL, SAID METHOD COMPRISING THE STEPS OF APPLYING TO THE FIBERS AN AQUEOUS SOLUTION CONTAINING FORMALDEHYDE, METHYL CELLULOSE, AND A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF UREA AND UREA DERIVATIVES, THE CONTENT OF METHYL CELLULOSE IN SAID SOLUTION BEING GREATER THAN THAT OF ANY OF THE OTHER INGREDIENTS.
 3. A PROCESS, AS RECITED IN CLAIM 1, IN WHICH THE AQUEOUS SOLUTION IS SPRAYED ONTO THE FIBERS WHILE IN A STATE OF SUSPESNION. 